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[bug fixing] Edge case of the double ended queue #9823

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Merged
merged 2 commits into from
Oct 5, 2023
Merged

[bug fixing] Edge case of the double ended queue #9823

merged 2 commits into from
Oct 5, 2023

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Jiang15
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@Jiang15 Jiang15 commented Oct 5, 2023

Describe your change:

I found a bug in double_ended_queue.py:
There is an error when popping the queue with only one element.
Code:

  dq = Deque([3])
  dq.popleft()

Error in dq.popleft()

self._front.prev_node = None
AttributeError: 'NoneType' object has no attribute 'prev_node'

same as the pop:
code:

dq = Deque([3])
dq.pop()

Error in dq.pop()

self._back.next_node = None
AttributeError: 'NoneType' object has no attribute 'next_node'

The fixing is to set both front and back pointers to None if there is only one element left in the queue before popping
I have written the test cases in the code and the tests are passed.

  • Add an algorithm?
  • Fix a bug or typo in an existing algorithm?
  • Documentation change?

Checklist:

  • I have read CONTRIBUTING.md.
  • This pull request is all my own work -- I have not plagiarized.
  • I know that pull requests will not be merged if they fail the automated tests.
  • This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
  • All new Python files are placed inside an existing directory.
  • All filenames are in all lowercase characters with no spaces or dashes.
  • All functions and variable names follow Python naming conventions.
  • All function parameters and return values are annotated with Python type hints.
  • All functions have doctests that pass the automated testing.
  • All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
  • If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

@algorithms-keeper algorithms-keeper bot added enhancement This PR modified some existing files awaiting reviews This PR is ready to be reviewed labels Oct 5, 2023
tianyizheng02
tianyizheng02 reviewed Oct 5, 2023
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Thanks for the fix!

@tianyizheng02 tianyizheng02 merged commit 55ee273 into TheAlgorithms:master Oct 5, 2023
@algorithms-keeper algorithms-keeper bot removed the awaiting reviews This PR is ready to be reviewed label Oct 5, 2023
sedatguzelsemme pushed a commit to sedatguzelsemme/Python that referenced this pull request Sep 15, 2024
@Jiang15 @sedatguzelsemme
[bug fixing] Edge case of the double ended queue (TheAlgorithms#9823)
cdde089 
* fix the edge case of the double ended queue pop the last element

* refactoring doc

---------

Co-authored-by: Jiang15 <[email protected]>
@isidroas isidroas mentioned this pull request Jan 25, 2025
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@Jiang15 @tianyizheng02